Hi. I've been thinking about this too.
I have a variation that I think would work...
8 empires:French, Russian, English, Austo-Hungarian, Ottoman, Swedish, Spanish, German (Prussian?).
8 static capital cities:Paris, St. Petersburg, London, Trieste, Constantinople, Stockholm, Madrid, Berlin
Each
capital city is worth
8 armies per turn. If you hold all
five territories in your empire you get an additional 4 (4 for any additional "empire" you hold as well). you also get 4 armies for holding a foreign capital. if you lose your capital city to an enemy you have three turns to retrieve it. if you do not get it back, then the player that holds your capital city the end of your third capital-less turn, gets all of your holdings. your armies turn into his/her armies.
other considerations:
in the 1986 version of castle risk you could attack by sea by playing the Admiral card. Since we don't have that ability via ConquerClub, i recommend dicing up the seas into a variety of tiles. Many of them will be coastal waters that you can use for defense. Some will be high seas that you can use to cover more ground. The oceans will be worth
no bonus, but will serve as a means to project power across the board - you can develop a naval expeditionary force.
Some territories will be neutral (in my beta map Italy, Switzerland, and Portugal). If you control the neutrals you get a small bonus (+2).
To Start the game:each player gets a capital city at random. all other squares are neutral (similar to the Feudal War map).
To win:
The victorious player must control all opponents capitals. The final capital must be held for 3 turns before the game ends.
Here is an image of the 1986 game set. I have developed a map loosely based on this, but i included Iceland and North Africa.

I will upload my map soon. What do you guys think?